1. Field of the Invention
The present invention relates to a method of producing a decorative pattern on a surface of a layer of a material, which may, for example, be used for making plates, such as roofing plates, panels, tiles, tile blocks and other building blocks and other similar articles.
2. Description of the Prior Art
It is known to impress decorative patterns in the outer surfaces of bricks and building blocks by means of rotating brushes having relatively stiff bristles, the free ends of which engage with and roughen the surfaces of the bricks or building blocks while the material thereof is in a plastic condition before the bricks or building blocks are fired or set, vide for example Swedish Pat. No. 73,039 and U.S. Pat. No. 1,293,076. German Offenlegungsschrift No. 2,442,070 discloses an apparatus for providing a stripe structure on the surface of extruded ceramic plates. In this known apparatus, the surface of the extruded plate passes and engages with a comb or brush and with a sponge arranged downstream thereof. By these known methods and apparatus it is possible to produce plates, bricks and building blocks with a surface structure which is very uniform. As the surface structure or surface pattern of slate and other natural materials is normally not uniform, but comprises random and differently sbaped depressions, the known methods and apparatus are not able to imitate such natural surface patterns or to make other non-uniform surface structures or patterns.